The present invention relates generally to methods and devices for cardiac surgery, and specifically to methods and apparatus for revascularization, particularly for transmyocardial laser revascularization (TMR).
TMR is a technique, known in the art, for creating channels in ischemic heart tissue, typically in the left ventricular wall of the heart, to improve the blood supply to ischemic myocardium. The technique is described, for example, by Mirhosein, et al., in an article entitled xe2x80x9cTransmyocardial Laser Revascularization: A Review,xe2x80x9d in the Journal of Clinical Laser Medicine and Surgery, vol. 11 (1993), pages 15-19, and by Bonn, in an article entitled xe2x80x9cHigh-power lasers help the ischaemic heart,xe2x80x9d in The Lancet, vol. 348 (1996), page 118, which are incorporated herein by reference.
In TMR, as is known in the art, a computer-controlled laser is used to drill holes about 1 mm in diameter in the myocardium, communicating with the left ventricle, at a typical density of about one hole per square centimeter. Typically, the laser beam is delivered to the epicardium through an incision in the chest and the pericardium that exposes the beating heart. The laser, typically a CO2 laser or, alternatively, an excimer or Ho:YAG laser, fires pulses of about 1000W, which photovaporize the myocardium and create channels through the endocardium into the ventricle. Blood at the outer, epicardial openings of the channels typically clots after a few minutes, but the inner portions of the channels, communicating with the ventricle, remain patent. It is hypothesized that during systole, blood flows through these channels into naturally-existing myocardial sinusoids, supplementing the impaired arterial blood supply.
Particularly when a CO2 laser is used, the laser is generally synchronized to the patient""s ECG, so as to fire its pulse during systole, in the refractory period of the heart cycle. Firing the laser pulse at other points in the heart cycle can cause undesirable arrhythmias. The heart rate, myocardial thickness and other factors are used to determine the optimum energy level for each laser pulse.
U.S. Pat. Nos. 5,380,316 and 5,554,152, to Aita, et al., which are incorporated herein by reference, describe methods for intra-operative myocardial revascularization using an elongated, flexible lasing apparatus, which is inserted into the chest cavity of the patient. The distal end of the apparatus is directed to an area of the exterior wall of the heart adjacent to a ventricle and irradiates the wall with laser energy to form a channel through the myocardium.
U.S. Pat. No. 5,389,096, to Aita, et al., which is also incorporated herein by reference, describes methods and apparatus for percutaneous myocardial revascularization (PMR). A deflectable, elongated lasing apparatus is guided to an area within the patient""s heart, and the distal end of the apparatus is directed to an area of interest in the inner wall of the heart. The wall is irradiated with laser energy to form channels therein, preferably without perforating the epicardium.
Since in PMR the channels are drilled from the inside of the heart outwards, there is no need for the channels to penetrate all the way through the heart wall, unlike more common TMR methods, in which the channels are drilled from the outside in. In other respects, however, the effects of PMR on the heart are substantially similar to those of TMR. Therefore, in the context of the present patent application, the term TMR will be used to refer to both extracardial and intracardial methods of laser revascularization of the myocardium.
It is an object of the present invention to provide improved methods and apparatus for TMR.
It is a further object of some aspects of the present invention to provide improved control over the TMR laser drilling procedure, and specifically to control the depth and direction of drilling.
In accordance with some aspects of the present invention, holes are drilled into the myocardium at controlled, substantially predetermined angles. Preferably, the holes are drilled at oblique angles, so as to produce longer channels through the tissue. These longer channels communicate with a greater volume of the myocardium than do channels drilled at approximately right angles to the heart wall, as are known in the art. The oblique channels thereby enhance the perfusion of ventricular blood in the tissue, and may communicate with greater numbers of myocardial sinusoids than do right-angle channels.
It is still another object of some aspects of the present invention to provide methods for mapping and sensing physiological signals in the heart tissue, to be used in conjunction with TMR to adapt and optimize the drilling procedure for the local conditions prevalent in the drilling area in the heart under treatment.
In preferred embodiments of the present invention, a catheter for use in TMR treatment comprises an optical or infrared waveguide and at least one sensor, adjacent the catheter""s distal end. The catheter has a distal end, which is surgically inserted into the body and brought into engagement with a surface of the heart muscle, and a proximal end, which is coupled to a console outside the body. The waveguide, preferably an infrared optical fiber, as is known in the art, receives a beam from a high-power laser preferably a pulsed CO2 laser, Ho:YAG or excimer laser, as are known in the art, at the proximal end of the catheter, and directs it at the heart surface. The console receives and analyzes signals from the sensor, in order to guide and control the treatment.
In some preferred embodiments of the present invention, the catheter is inserted into a chamber of the heart, preferably into the left ventricle, by passing the catheter percutaneously through the arterial system. Alternatively, the catheter may be passed through the venous system into the right atrium and ventricle. In these preferred embodiments, the catheter engages the endocardium, and the laser is fired to drill holes into the myocardium from the inside. Preferably, these holes are drilled only to a limited depth, without penetrating the epicardium. Further preferably, the holes are drilled to a depth that is generally sufficient to communicate with the myocardial sinusoids, preferably no more than 8 mm deep, measured in a direction perpendicular to the surface of the heart tissue. More preferably the holes are drilled to a depth of no more than 6 mm, and most preferably, to a depth of about 3 mm.
In other preferred embodiments of the present invention, the catheter is inserted through a surgical incision in the chest wall and then through the pericardium. The catheter engages the epicardium of the left ventricle, and the laser is fired to drill holes through the myocardium and into the left ventricle, guided by the signals received from the sensor at the catheter""s distal end.
Preferably, the holes drilled in the heart tissue are approximately one millimeter in diameter. In some preferred embodiments of the present invention, the holes have elliptical, rather than circular cross-section. The elliptical holes have a greater surface area than circular holes of the same cross-sectional area, and therefore may be more effective in enhancing the perfusion of blood into the myocardium. Preferably, the waveguide is flared at the distal end of the catheter to provide an output laser beam profile having a shape and diameter substantially similar to the desired shape and diameter of the holes to be drilled.
In some preferred embodiments of the present invention, the laser is focused onto the heart tissue at a sufficiently high power density to generate shock waves in the tissue. For CO2 laser irradiation, the power density is preferably at least 1 MW/cm2. The shock waves cooperate with the photovaporization effect of the laser beam incident on the tissue to drill holes in the myocardium which, it is believed, are more effective in improving perfusion of the myocardium than holes drilled by photovaporization (or ablation) alone. Preferably, at least a portion of the distal end of the catheter, adjacent to the waveguide, is shaped to focus and concentrate shock waves generated by the laser beam into the heart tissue.
In some preferred embodiments of the present invention, the catheter includes a surgical cutting instrument at its distal end. The cutting instrument is used to make an incision, of a controlled, limited depth, through the outer tough layer of the heart tissue, i.e., in the endocardium in embodiments in which the catheter is inserted into the ventricle, or in the epicardium in embodiments in which the catheter is inserted through the chest wall and pericardium. The laser is then fired through the incision in the outer tough layer to drill a hole through the softer inner layers of myocardium. In consequence, a substantially lower-energy laser pulse can be used to produce a hole of desired depth.
Preferably, in these preferred embodiments, the optical waveguide in the catheter is retracted inside the catheter while the cutting instrument makes its incision, and is then extended distally out of the catheter to deliver laser energy into the incision. In this manner, the laser pulse is delivered with greater precision to the desired location in the myocardium.
In some preferred embodiments of the present invention, the catheter is controlled so as to direct the laser beam into the myocardium at a predetermined angle. In contrast to these preferred embodiments, in catheter-based methods and systems known in the art, it is generally not possible to substantially control the beam angle.
In these preferred embodiments, the laser beam is preferably directed obliquely, i.e., at a high angle of incidence with the surface of the heart (measured relative to a direction perpendicular to the surface). Preferably, the angle of incidence is greater than 20xc2x0, more preferably greater than 40xc2x0, and most preferably greater than 60xc2x0. The high angle of incidence of the laser beam causes a hole to be drilled at a correspondingly high angle. The resulting channel through which ventricular blood will flow into the myocardium will generally be longer and is therefore likely to communicate with greater numbers of sinusoids than would a channel at or near normal incidence, as is known in the art. The angle of incidence of the laser beam upon the surface of the heart is most easily and accurately controlled when the catheter is inserted through the chest wall and pericardium and engages the epicardium.
In some of these preferred embodiments, the catheter is configured such that the laser beam is directed out of the distal end thereof in a predetermined oblique angular direction relative to the long axis of the catheter. Optical techniques and devices for such oblique beam delivery are known in the art. When the distal end of such a catheter is brought into engagement with the surface of the heart tissue in a direction substantially perpendicular thereto, for example, the laser beam will be directed into the tissue substantially at the predetermined oblique angle.
Alternatively, a distal portion of the catheter, including the distal end thereof, may be positioned against the heart wall in a substantially tangential position relative thereto. The laser beam is directed obliquely out of the distal end into the heart tissue, substantially as described above. Methods and devices for positioning the catheter in a desired position and orientation in such tangential contact with the heart tissue are described in a U.S. provisional patent application entitled xe2x80x9cConformal Catheter,xe2x80x9d filed Jan. 3, 1997, which is assigned to the assignee of the present patent application and whose disclosure is incorporated herein by reference. Alternatively or additionally, the catheter may be positioned with the assistance of imaging techniques, such as fluoroscopy, or a position sensor fixed in the catheter, as are known in the art.
In some preferred embodiments of the present invention, the catheter includes a lumen for vacuum suction, which is coupled to a vacuum pump or other suitable suction device, as is known in the art, at the proximal end of the catheter. The suction lumen has an outlet at the distal end of the catheter, which is preferably immediately adjacent to the waveguide. After the distal end is properly positioned in contact with the heart tissue at a point into which a hole is to be drilled, the pump or suction device is activated. A partial vacuum is thus created at the distal outlet of the lumen, which holds the distal end in place while the laser is fired.
Additionally or alternatively, the lumen may be used for passing surgical tools, such as J-shaped retractable barbs, grasping tools and screws, to the outlet at the distal end of the catheter. These tools may be used for performing surgical procedures in the heart, in conjunction with the TMR operation.
In some preferred embodiments of the present invention, the at least one sensor at the distal end of the catheter comprises a position and/or orientation sensor. Preferably, this sensor comprises a plurality of non-concentric coils, which generate signals responsive to an externally-applied, time-varying, magnetic field, as described in PCT patent publication number WO96/05768, filed Jan. 24, 1995, and incorporated herein by reference. Alternatively, the position sensor may comprise a single coil, as described in U.S. Pat. No. 5,391,199, which is also incorporated herein by reference, or several such coils. The coil signals are analyzed to determine position and/or orientation coordinates of the catheter, preferably six-dimensional position and orientation coordinates, as described in the above mentioned PCT publication.
Further alternatively, the position sensor may comprise any suitable type of miniature position and/or orientation sensor known in the art, such as RF sensors, DC magnetic field-responsive sensors, ultrasound sensors, or a Carto system, available from Biosense, Ltd., Tirat Hacarmel, Israel.
The coordinates of the catheter that are derived from the position sensor are used to ascertain that the distal end of the catheter engages the heart tissue at a desired, preferably predetermined position and/or orientation before the laser is fired. Preferably, the coordinates are registered with a map of the heart acquired, for example, by ultrasound imaging. Alternatively, the map may be acquired using a mapping catheter, such as are described in U.S. patent application Ser. No. 08/595,365 and in PCT patent application US95/01103, which are assigned to the assignee of the present patent application, and whose disclosure is incorporated herein by reference.
Preferably, a second, reference catheter, which includes a position sensor of the same or a similar type to that of the TMR catheter described above, is inserted into the heart at a fixed, known position relative thereto. Position and/or orientation coordinates of this reference catheter are used to transform the coordinates of the TMR catheter to a frame of reference that is fixed to the heart. In this way, errors in positioning the TMR catheter that may result from movement of the heart are reduced.
Alternatively, a reference element, including a position sensor, may be placed on the surface of the body and used to transform the coordinates of the TMR catheter to a frame of reference that is fixed to the body. Errors in positioning the TMR catheter due to movement of the body are thus reduced, without the need for the second catheter in the heart, although errors due to movement of the heart cannot be corrected in this fashion.
In some of these preferred embodiments, signals received from the position sensor are used to gate the operation of the laser, as described, for example, in U.S. provisional patent application 60/011,720, which is assigned to the assignee of the present patent application, and whose disclosure in incorporated herein by reference. The laser is allowed to fire only when it is determined that the distal end of the catheter is in the proper position and orientation to drill a desired hole in the heart tissue.
Preferably, the console is pre-programmed with position and orientation coordinates of a plurality of such holes. The catheter is moved over the surface of the heart tissue, and the laser is gated to fire whenever the catheter reaches the coordinates of one of the holes. After a hole is drilled, its position is preferably marked, for example, in computer memory, on a map of the heart, as described above.
In some preferred embodiments of the present invention, the at least one sensor at the distal end of the catheter comprises an electrode, which senses and generates signals responsive to local electrical potentials in the heart tissue. Preferably, signals received from the electrode are used to trigger the firing of the laser pulse, so that the pulse is fired during the appropriate portion of the systolic, refractory period of the tissue that the catheter is engaging. In this manner, local variations in electrical activation and contraction of the heart muscle can be taken into account, to fire the laser at the optimal moment, with greater precision than is possible when the eternally-measured ECG signal is used for this purpose, as is known in the art.
In some of these preferred embodiments, the electrode is used to generate a viability map of the heart, as described in the above-mentioned U.S. patent application Ser. No. 08/595,365, and in U.S. provisional patent application No. 60/009,769, which is assigned to the assignee of the present patent application, and whose disclosure is incorporated herein by reference. Alternatively, the viability map may be generated using a different catheter inside the heart, which is then preferably removed before inserting the TMR catheter.
The viability map is used to identify areas of the heart tissue that are ischemic but still viable, as against other areas that either have adequate perfusion or that have lost their viability due to infarction or prolonged ischemia. The map is preferably based on electrophysiological data, indicative of the flow of activation signals through the heart tissue. Alternatively, the map may be derived from biomechanical data, such as variations in the thickness of the heart wall between systolic and diastolic stages of the heart cycle, or from a combination of biomechanical and electrophysiological data. Preferably, the TMR treatment is performed in the ischemic but still viable areas.
In some preferred embodiments of the present invention, the at least one sensor at the distal end of the catheter comprises an ultrasound transducer. Preferably, the transducer generates signals responsive to the thickness of the heart tissue adjacent to the position of the distal end of the catheter. The thickness-responsive signals are preferably used in determining a desired depth to which the holes in the myocardium are to be drilled. The laser beam energy is then controlled so as to produce holes of this predetermined depth.
Further preferably, signals generated by the transducer are used to monitor the depths and/or directions of holes drilled by the laser.
Additionally or alternatively, the ultrasound signals are used to monitor the thickness of the heart tissue dynamically. As is known in the art, the tissue cyclically thickens during systole and thins during diastole. The laser is triggered so as to fire pulses while the heart tissue is, preferably, substantially at the thickest point in the cycle or, alternatively, at the thinnest point in the cycle. Such thickness-triggered drilling can take the place of laser triggering based on ECG or other electrophysiological signals, potentially enhancing the accuracy and safety of the operation.
Alternatively, in preferred embodiments of the present invention wherein the catheter includes a position and/or orientation sensor adjacent to its distal end, signals received from this sensor may be used to detect movement of the heart wall. The laser is then triggered in response to the rapid, contractile movement of systole.
To summarize, in preferred embodiments of the present invention, the catheter includes laser beam delivery optics and one or more of a variety of sensors, as described above. The one or more sensors preferably include at least one of the following types of sensors, singly or in combination: electrophysiological sensing electrodes; position sensors; ultrasound transducers; other sensors for measuring heart wall thickness, as are known in the art; other sensors for measuring heart tissue viability, as described in the above-mentioned U.S. patent application Ser. No. 08/595,365 or U.S. provisional patent application No. 60/009,769, or otherwise known in the art; and other sensors, known in the art, for measuring perfusion of the heart tissue.
In some preferred embodiments of the invention, the system is triggered in response to other characteristics. For example, the radiation may be triggered in response to one or more of the phase of heart cycle or local mechanical characteristics of the of the heart such as: the velocity of the sensor or its acceleration.
Alternatively or additionally, in some preferred embodiments of the invention, the system is inhibited until a stability condition is met. For example, the radiation may be inhibited unless one or more of the heart cycle, heart rhythm, stability of the position of the distal end of the probe on the heart tissue, stability of the cyclical angular relationship between the distal end of the probe and the heart tissue, stability of the contact between the probe and the tissue.
Some of these conditions may be determined from measurements external to the heart and all of them can be made based on measurements made on the heart itself.
In some preferred embodiments of the present invention, as described above, such catheters are inserted percutaneously and are used to drill channels in the heart tissue endocardially, i.e., from inside a chamber of the heart into the myocardium. In other preferred embodiments, such catheters are inserted through the chest wall and drill channels epicardially, through the myocardium and into a chamber of the heart.
Although in the preferred embodiments described above, the catheter includes a sensor at its distal end, it will be appreciated that some of the methods of the present invention may be applied to perform TMR with greater effectiveness or safety, even without the use of the sensor. For example, in accordance with the principles of the present invention, any suitable laser may be used to drill oblique channels in the myocardium from inside or outside the heart. In this case, the catheter is preferably positioned to drill channels based on a viability map, produced in advance of the TMR procedure.
It should be understood that while the invention is described herein in the context of TMR as defined herein and in particular to the drilling of holes using laser light, its application is broader and includes the control of irradiation of the heart in general and in particular to the formation of one or more irradiation paths within the myocardium by laser light or by other forms of irradiation.
Furthermore, it should be understood that the term xe2x80x9ccoordinatexe2x80x9d as used herein means any of the six coordinates of position and orientation, e.g., the three position and the three orientation coordinates.
There is thus provided in accordance with a preferred embodiment of the invention, an elongate probe for providing irradiation treatment of the heart, said probe having a distal end for engaging heart tissue of a subject, comprising:
a waveguide, which conveys radiation to the heart tissue for irradiation thereof; and
a sensor, adjacent the distal end of the probe, which generates signals for use in controlling the treatment.
Preferably, the probe has a longitudinal lumen, which communicates with an orifice in a vicinity of the distal end of the probe. Preferably, the lumen is coupled proximally to a suction device, so as to create a partial vacuum at the orifice. In one preferred embodiment of the invention a surgical cutting instrument is passed through the lumen to the distal end of the probe.
In a preferred embodiment of the invention, the waveguide is extendible distally out of the distal end of the probe.
In a preferred embodiment of the invention the distal end of the probe comprises a generally concave outer surface, for focusing shock waves distal to the distal end, in a vicinity of the waveguide. Preferably, the concave outer surface comprises a fiberoptic faceplate formed at the distal end of the waveguide.
In a preferred embodiment of the invention, the probe further comprises a focusing lens, which focuses the radiation along an axis related to the probe. Preferably, the lens focuses the radiation such that the radiation forms a beam having a generally elliptical profile.
In a preferred embodiment of the invention, the radiation is directed out of the probe at a predetermined oblique angle relative to the long axis of the probe. Preferably, the probe comprises an optical deflection element, which directs the radiation out of the probe at the oblique angle.
Preferably the sensor comprises at least one electrode, which receives electrophysiological signals from the heart tissue.
Alternatively or additionally the sensor comprises an ultrasound transducer. Preferably, the ultrasound transducer emits a steerable ultrasound beam in a generally distal direction relative to the distal end of the probe.
Alternatively or additionally the sensor comprises a coordinate sensor. Preferably the coordinate sensor generates signals indicative of six-dimensional position and orientation coordinates of the probe, the coordinate sensor comprises one or more coils, which generate signals responsive to an externally-applied magnetic field.
There is further provided, in accordance with a preferred embodiment of the invention, apparatus for treatment of the heart, comprising:
a probe according as described above;
a radiation source, coupled to the waveguide in the probe; and
a control unit, comprising an irradiation actuator, which receives the signals from the sensor in the probe and controls the source responsive to the signals.
Preferably the apparatus comprises a positioning actuator which steers the distal end of the probe so as to irradiate the heart tissue at a desired coordinate.
In a preferred embodiment of the invention the apparatus comprises:
a control unit including a positioning actuator, which receives the signals from the coordinate sensor in the probe and controls the coordinates of the distal end of the probe responsive to the signals.
Preferably, the control unit determines position coordinates of the distal end of the probe based on the signals and the positioning actuator steers the probe based on the position coordinates so as to engage the heart tissue in a desired position.
Preferably, the control unit determines orientation coordinates of the distal end of the probe based on the signals and the positioning actuator steers the probe based on the orientation coordinates so as to engage the heart tissue at a desired angle. Preferably, the control unit compares the coordinates to a predetermined value and triggers the radiation source only when the coordinates are substantially equal to the predetermined value.
In a preferred embodiment of the invention the apparatus comprises according to any of claims 18-23, and comprising a reference probe, wherein the control unit determines coordinates of the reference probe and refers the coordinates of the probe to the coordinates of the reference probe. Preferably, the control unit controls the probe based on the coordinates so as to irradiate the tissue at a desired angle.
There is further provided in accordance with a preferred embodiment of the invention apparatus for treatment of the heart, comprising:
an elongate probe having a distal end for engaging heart tissue of a subject, and comprising a waveguide, which conveys radiation to the heart tissue for treatment thereof;
a source of radiation, coupled to the waveguide in the probe; and
a control unit comprising a positioning actuator which controls the coordinates of the probe so as to irradiate the surface at a controllable angle.
Preferably, the probe also comprises a sensor adjacent its distal end, wherein said sensor supplies signals to the control unit.
In a preferred embodiment of the invention the control unit triggers the radiation source responsive to variations in the signals.
Preferably, the control unit controls the radiation source to drill channels to a desired depth. Preferably, the control unit determines the depth of the channels, based on the signals, so as to control the radiation source to drill channels to a desired depth.
In a preferred embodiment of the invention, the control unit triggers the radiation source responsive to variations in the signals. Preferably, the control unit triggers the radiation source responsive to the phase of the heart cycle.
In a preferred embodiment of the invention the control unit triggers the radiation source based on a local mechanical characteristic of the heart. Preferably the local mechanical characteristic includes one or more of a position of a sensor coupled to a portion of the to the heart; a velocity of a sensor coupled to a portion of the heart; an acceleration of a sensor coupled to a portion of the heart; and an orientation of a sensor with respect to a portion of the heart.
In a preferred embodiment of the invention, the control unit triggers the radiation source only when a stability condition is met. Preferably, the stability condition includes one or more of stability of the heart cycle to within a given stability; stability of the heart rhythm to within a given stability; stability of the position of the distal end of the probe on the tissue to within a given stability; stability of the cyclical angular relationship between the distal end of the probe and the tissue to within a given stability; and stable contact between the probe and the tissue.
The stability condition may be derived from a measurement made external to or internal to a patient being treated, as appropriate.
In a preferred embodiment of the invention the probe includes a lumen and the apparatus includes a source of irrigating liquid which supplies said liquid for irrigating the tissue.
In a preferred embodiment of the invention the radiation source is a laser.
There is further provided, in accordance with a preferred embodiment of the invention, apparatus for treatment of the heart comprising:
means for applying a treatment at successive positions on the heart; and
a memory in which the successive positions are stored.
In a preferred embodiment of the invention the means for applying includes a probe; and the apparatus comprises: a display which displays a map of the heart; and a controller which marks the display of the heart with a treatment position when a treatment is applied.
In a preferred embodiment of the invention, the display indicates the position of each of the successive treatments.
Preferably, the treatment comprises irradiation of the heart with a radiation source. Preferably the radiation source is a laser. Alternatively or additionally the treatment comprises the formation of irradiation paths within the myocardium. Alternatively or additionally the treatment comprises drilling of holes in the myocardium.
There is further provided, in accordance with a preferred embodiment of the invention, a method for treatment of the heart, comprising:
bringing a probe into engagement with a surface of the heart tissue of a subject; and
irradiating the heart tissue via the probe at a controllable angle, which may be an oblique angle, relative to the surface, which may be either the epicardium or the endocardium of the heart.
In preferred embodiments of the invention the angle is at least 20xc2x0, 40xc2x0 or 60xc2x0 relative to an axis perpendicular to the surface.
In a preferred embodiment of the invention irradiating comprises generating shock waves in the heart tissue, preferably, concentrating the shock waves in the heart tissue by reflection of the waves from a concave surface of the probe.
There is further provided, in accordance with a preferred embodiment of the invention a method for heart treatment, comprising:
bringing a probe, into engagement with a surface of the heart tissue of a subject;
irradiating the tissue with radiation via the probe, wherein the radiation generates shock waves in the heart tissue; and
concentrating the shock waves in the heart tissue by reflection of the waves from a concave surface of the probe.
In preferred embodiments of the invention irradiation includes photovaporizing the tissue. Alternatively or additionally the irradiation is laser radiation.
Preferably, irradiation comprises forming a plurality of irradiation paths in the tissue. In a preferred embodiment of the invention the paths have a generally elliptical cross-section.
There is further provided, in accordance with a preferred embodiment of the invention a method of treatment of the heart, comprising:
bringing a probe into engagement with a surface of the heart tissue of a subject;
forming one or more irradiation paths having an elliptical cross-section in the heart tissue by irradiating the heart via the probe.
Preferably the irradiation is laser irradiation. Alternatively or additionally, forming an irradiation path comprises drilling a channel. In a preferred embodiment of the invention the method comprises drilling the channels to a depth of no more than 10 mm, measured in a direction perpendicular to the surface of the endocardium. More preferably the depth is not more than 6 or approximately 4 mm.
In a preferred embodiment of the invention bringing the probe into engagement with the surface of the heart tissue comprises bringing a distal portion of the probe into tangential contact with the heart tissue, and wherein irradiating the heart tissue comprises directing radiation from the probe at an angle relative to a long axis of the probe.
Preferably, the method includes exerting suction through a lumen in the probe so as to anchor the probe to the tissue in a desired position.
In a preferred embodiment of the invention the method comprises controlling the irradiation responsive to the characteristic that is sensed.
There is further provided, in accordance with a preferred embodiment of the invention, a method for treatment of the heart, comprising:
bringing a probe, into engagement with a surface of the heart tissue of a subject;
sensing a local characteristic of the heart; and
irradiating the heart via the probe, while controlling the irradiation responsive to the characteristic that is sensed.
Preferably, sensing the characteristic of the heart comprises sensing electrical potentials in the heart tissue.
Preferably, controlling the irradiation responsive to the characteristic comprises triggering the irradiation responsive to the potentials.
In a preferred embodiment of the invention sensing the characteristic of the heart comprises producing a viability map of the heart and/or receiving ultrasound signals from the tissue and/or analyzing the ultrasound signals to determine the thickness of the heart tissue in a vicinity of the probe. Preferably, controlling the irradiation responsive to the characteristic comprises triggering the irradiation responsive to variations in the thickness. Preferably, sensing the characteristic of the heart tissue comprises analyzing the ultrasound signals to determine the depth of the channels.
Preferably, controlling the irradiation responsive to the characteristics comprises controlling the irradiation to drill channels having a desired depth.
In a preferred embodiment of the invention the method comprises receiving and analyzing signals from a coordinate sensor coupled to the probe to determine coordinates of the probe, wherein bringing the probe into engagement with the surface of the heart tissue comprises controlling the coordinates of engagement of the probe based on the coordinates.
There is further provided, in accordance with a preferred embodiment of the invention a method for treatment of the heart, comprising:
receiving and analyzing signals from a coordinate sensor coupled to a probe to determine coordinates of the probe;
bringing the probe into engagement with a surface of the heart tissue of a subject, while controlling the coordinates of engagement of the probe based on the signals; and
forming one or more irradiation paths in the heart tissue by irradiating the heart tissue with radiation via a waveguide in the probe.
Preferably, receiving and analyzing the signals to determine the coordinates of the probe comprises determining six-dimensional position and orientation coordinates of the probe.
Preferably controlling the coordinates of engagement of the probe comprises controlling the probe""s angular orientation relative to the surface of the heart tissue.
Preferably, receiving and analyzing the signals from the coordinate sensor comprises receiving and analyzing signals generated in response to a magnetic field applied to the probe.
In a preferred embodiment of the invention the method comprises registering the coordinates of the probe with a map of the heart. Preferably, registering the coordinates with the map of the heart comprises registering the coordinates with a viability map of the heart.
In a preferred embodiment of the invention, the method comprises recording the coordinates of the one or more irradiation locations relative to the map of the heart.
In a preferred embodiment of the invention the method comprises selecting probe target coordinates corresponding to at least one of the irradiation paths to be formed in the heart tissue, wherein forming the paths comprises triggering the irradiation when the coordinates of the probe correspond to the target coordinates of the at least one of the channels.
Preferably forming irradiation paths comprises triggering the irradiation responsive to a change in the signals received from the coordinate sensor indicative of systolic contraction of the heart.
Preferably the method further comprises:
fixing a reference probe to the heart; and
receiving and analyzing signals from the reference probe to determine coordinates thereof,
wherein receiving and analyzing the signals from the position sensor coupled to the probe to determine the coordinates of the probe comprises referring the coordinates of the probe to the coordinates of the reference probe.
The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which: